Conversion of hydrocarbon oil to a synthetic natural gas

ABSTRACT

A crude hydrocarbon oil or gas oil is cracked with a &#39;&#39;&#39;&#39;used&#39;&#39;&#39;&#39; cracking catalyst having a high metal content under conditions of severity to produce gasoline and lighter products to an optimum extent. Effluent is cooled to obtain a gasoline fraction with large amounts of H2 and light gases and a heavier product stream which is recycled to the cracking operation. Gasoline and higher components are dehydrosulfurized, using generated hydrogen for the purpose. Thus treated stream is cooled to obtain a liquid and a gas stream. A portion of the gas stream is used as a hydrogenrich gas for the catalytic hydrodesulfurization. Another portion is treated to remove H2S therefrom and thus treated gas and liquid obtained upon the cooling, after some preheat, are passed to a synthetic natural gas reactor, preferably after further treatment to produce a stream containing less than about one part per million of sulfur. The process is self-sustaining in hydrogen. Coke deposited on catalyst on regeneration yields sufficient heat to supply steam requirement for Synnat process.

United States Patent 11 Johnson [451 Oct. 29, 1974 CONVERSION OFHYDROCARBON OIL TO A SYNTHETIC NATURAL GAS Marvin M. Johnson,Bartlesville, Okla.

Assignee: Phillips Petroleum Company, Bartlesville, Okla.

Filed: Dec. 27, 1972 Appl. No.: 318,701

[75] Inventor:

[5 6] References Cited UNITED STATES PATENTS 11/1970 Smith, Jr 208/895/1973 Carr et al 48/213 X Primary Examiner-R. E. Serwin [5 7] ABSTRACTA crude hydrocarbon oil or gas oil is cracked with a used crackingcatalyst having a high metal content under conditions of severity toproduce gasoline and lighter products to an optimum extent. Effluent iscooled to obtain a gasoline fraction with large amounts of H and lightgases and a heavier product stream which is recycled to the crackingoperation. Gasoline and higher components are dehydrosulfurized, usinggenerated hydrogen for the purpose. Thus treated stream is cooled toobtain a liquid and a gas stream. A portion of the gas stream is used asa hydrogenrich gas for the catalytic hydrodesulfurization. Anotherportion is treated to remove H 8 therefrom and thus treated gas andliquid obtained upon the cooling, after some preheat, are passed to asynthetic natural gas reactor, preferably after further treatment toproduce a stream containing less than about one part per million ofsulfur. The process is self-sustaining in hydrogen. Coke deposited oncatalyst on regeneration yields sufficient heat to supply steamrequirement for Synnat process.

4 Claims, 1 Drawing Figure NZYCOZ CRACKED GAS a I COMPRESSOR 2, i' lz 7AND LIGHT LIQUID AIR HYDROCARBONS CA c HYDRODESULFURIZATION ANDHYDROGENATION OF OLEFINS CRACKER '-2s 32 H2 GAS-OIL I HEAVY RICH GASHYDROCARBON COMPRESSOR 27 29 2- STEAM m as PREHEATER 5 34 GAS SEPARATORSYNNAT REACTOR 5 l \UQUID r H2S\ 1 PHASE -37 35- '54 49 as as 5l- 53- 4|55 LC 46 1 s2 ZnO 42 Bed 11 s REMOVAL umr 45 CONVERSION OF I-IYDROCARBONOIL TO A SYNTHETIC NATURAL GAS This invention relates to the productionof a synthetic natural gas. In one of its aspects it relates to aconversion of a crude oil or gas oil to a synthetic natural gas orgaseous fuel. In a further aspect of the invention, it relates to acombination of steps converting a crude oil or other liquid hydrocarbonsto a feed for a catalytic,

synthetic natural gas-producing operation.

cooled forming a liquid condensate and a hydrogen-' rich stream, aportion of the hydrogen-rich stream is cycled to the catalytichydrodesulfurization while another portion is subjected to treatment toremove therefrom H 8 whereupon it with liquid obtained in the lastmentioned cooling is passed to a synthetic natural gas-producingoperation. In another of its concepts, the invention provides anoperation as described wherein heavier reaction products obtained uponcooling the cracking effluent are recycled to the cracker to extinction.In a further concept of the invention, it provides a process asdescribed wherein the synthetic natural gas reactor feed stream issubjected to a final desulfurization to yield a feed stream containingless than about one part per million of sulfur. Further, still anotherconcept of the invention provides a process which in regenerating thecatalyst used to crack the feed stock in the cracking operation isregenerated and only regeneration provides sufficient heat to yieldsteam for operation of the synthetic natural gas producing step. In amore specific concept of the invention, the feed to the syntheticnatural gas producing reactor (SYNNAT a trademark) is a full rangenaphtha which permits obtaining high yields of fuel gas from the crudeoil.

I have conceived a combination of steps for producing a syntheticnatural gas or fuel involving steps as herein described which isself-sustaining in hydrogen requirement, i.e., there is no need toconvert a portion of the crude to hydrogen in a separate operation.Further, in the combination of steps, as herein described, cokedeposited on a cracking catalyst will yield on regeneration sufficientheat to provide the steam requirement for operation of the Synnatprocess. This includes waste heat recovery on all process stepsdescribed and suitably positioned heat exchange zones.

Calculations show that a crude with a I-I/C ratio of 1.786 will netapproximately 6.66 M SCF/B of feed of 754 Btu/SCF, which corresponds toa thermal efficiency of 80 percent over-all. The reaction sequence canbe generally depicted as follows:

1.08 C 1.08 4.07 N; l.O8 CO 4.07 N

2.65 cu +1.10 H2O 2. 10 cu, 0.55 co 0.5

The respective equations represent (I) the catalytic cracking reaction,(2) theregeneration of the catalyst, and (3) the conversion process thatoccurs in the Synnat unit. There is essentially no change in the HICratio in the desulfurization olefin saturation step.

The net gas yield and over-all thermal efficiency are dependent to anextent on the feed composition, employing of course conditions suitableto each, and lesser yields of product gas will be obtained from feedshigher in aromatic content. The approximate relationship betweencomposition of the feed and efficiency is shown in Table I.

TABLE I O I in It is an object of this invention to produce syntheticnatural gas or fuel. It is another object of the invention to provide aprocess for the production of a synthetic natural gas or fuel. It is afurther object of this invention to provide a combination of steps in aunitary operation permitting the conversion of a crude oil or gas oil toa synthetic natural gas, the operation being selfsustaining in heatrequired to generate steam used in the process.

Other aspects, concepts, objects and the several advantages of theinvention are apparent from a study of this disclosure, the drawing andthe appended claims.

ciently to condense therefrom substantially C and higher boilingproducts, desulfurizing gases and vapors thus obtained including any Cmaterial not separated therefrom while simultaneously hydrogenatingoletins contained therein, cooling to separate a hydrogen rich light gasfrom a liquid fraction, using a portion of said hydrogen rich light gasfor the hydrogenation of said olefins, subjecting another portion ofsaid hydrogenrich gas together with liquid obtained upon cooling thedesulfurized stream to a synthetic natural gasproducing operation forconversion to a natural gas or fuel.

In one embodiment of the invention which is now preferred, the C andhigher boiling materials obtained upon cooling of the catalytic crackingeffluent are recycled to the catalytic cracking operation. Also in saidembodiments the combined liquid and gas which has been treated to removeH S therefrom is passed to a further or final sulfur-removal step, forexample, through a zinc oxide bed, to produce a feed for the Synnatreaction zone containing less than about one part per million of sulfur.

Also according to the invention and as a feature thereof, the conditionsof operation including the cracking and regeneration of catalyst are soselected as to provide sufficient heat-from the regeneration of thecracking catalyst and from the Synnat reactor that the steamrequirements in the Synnat reactor can be met.

Conventional cracking catalyst such as synthetic or natural zeolites,synthetic or natural clays, bauxite, brucite, silica-alumina and thelike can be used in the practice of this invention. These catalysts areused under high severity conditions to produce a mixture ofhydrogen-rich light gas and naphtha. Thus used or spent known crackingcatalyst adapted to severely crack a heavier crude oil normally notsuited to producing a gasoline and containing up to about 2 weightpercent metals such as nickel, vanadium and iron, present as the oxide,in the catalyst, for example supported on a suitable carrier, e.g.,silica-alumina, a zeolite, etc., can be employed.

The oil is advantageously catalytically cracked at a temperature of fromabout 800 to l,300 F and preferably the cracking will be conducted at atemperature in the range of from about 900 to l,l F. The regeneration ofthe used catalyst is conducted in a temperature range of from aboutl,l00 to about l,400 F or even somewhat higher.

The catalytic cracking operation can employ a fixedbed, moving bed orfluid or other process.

In the second stage of the operation, the noncondensed gases and naphtharange hydrocarbons are hydrotreated using a hydrotreating catalyst,e.g., a nickel molybdate or equivalent catalyst to effect at least apartial desulfurization and complete saturation of olefins. The catalystused is any type of hydrogenation catalyst which functions in thepresence of sulfur, for example, sulfides or oxides of tungsten,molybdenum, chromium, vanadium, etc. A now preferred type of catalyst isa mixture or chemical combination of an oxide or sulfide of an irongroup metal with an oxide or sulfide of a metal of Group VlB, such as amixture of an oxide or sulfide of nickel or cobalt with an oxide orsulfide of molybdenum or tungsten. Especially preferred, now, is anickel molybdate or a cobalt molybdate catalyst. The catalyst ispreferably on a porous support selected from activated alumina or asilicaalumina cracking catalyst. These catalysts are known in the art.

The temperature in the hydrotreating step will usually be in the rangeof from about 500 to about 750 F. a temperature in the approximate rangeof from about 550 to about 650 F being now preferred. A pressure of fromabout 100 to about 2,000 psig can be used. A pressure of from about 200to 700 psig is now preferred. Hydrotreating of this kind is known in theart. in general.

A portion of the hydrogen-rich gas is recycled to remove the exothermicheat from the hydrodesulfurization reactor and to aid in thedesulfurization. This gas also hydrogenates the olefins as earlierexplained. The balance of the gas phase obtained from thehydrodesulfurization reactor is sent to a hydrogen sulfide removal step.e.g., a Girbotol unit to remove hydrogen sulfide from the gas. Thisoperation is described in Petroleum Refiner, September, 1960, page 267and is known as the Girbotol process.

Aqueous solutions of monoethanolamine and diethanolamine are generallyemployed in the Girbotol process for removal of hydrogen sulfide fromthe gases. The absorber normally operates at about F at the inlet and108 F at the outlet at about 300 psi pressure. The stripper in theGirbotol unit usually is operated at about 200 F and from about 5 toabout 10 psig pressure. One skilled in the art can select differentcondi tions depending on the results he wishes to reach.

The gas from the Girbotol unit is passed with the liquid stream obtainedin the separation of gases resulting from the hydrodesulfurizationeffluent and the combined gas and liquid stream is further desulfurizedas may be necessary. It is now preferred to contact the stream with azinc oxide or equivalent bed to remove trace amounts of hydrogensulfide. The thus obtained sulfide free gas, containing less than aboutone part per million of sulfur, is passed to the Synnat reactor. In thisreactor, a synthetic natural gas stream is produced.

The Synnat process is described in the art. Patents related to thisoperation are U.S. Pat. No. 3,506,417 issued Apr. 14, 1970, Harold J.Hepp and E. O. Box, Jr.; U.S. Pat. No. 3,506,4l8 issued Apr. 14, 1970,William G. Billings and U.S. Pat. No. 3,522,024 issued July 28, 1970,William G. Billings and William T. Nelson. The disclosures of thesepatents are incorporated herein.

The conditions for the Synnat operation now preferred in this inventionare a reforming temperature, which can vary appreciably, and which willbe usually in the range of from about 700 to l,000 F preferably in therange of from about 750 to 875 F. The reaction pressure will beordinarily in the range of from about 100 to about 2,000 psig,preferably 200-700 psig. The steam to hydrocarbon weight ratio will beordinarily at least about 1.2 to 1, generally in the range of from about1.211 to about 6:1.

Referring now to the drawing the feed hydrocarbon, for example, a WestTexas atmospheric gas oil, as described herein, is passed by l, 2, heatexchanger 3, and 4 into cracker 5. The temperature in cracker 5 is'maintained at a level of the order-of about 900 F. A catalyst, asdescribed herein, which has been used and which is one having a metalcontent is employed to maximize yields of C and lighter hydrocarbon.Other catalytic products including gases are formed.

Spent catalyst is passed by 6 together with air entering at 7 into aregenerator 8 at which a catalyst is regenerated under conventionalconditions which include a temperature of the order of about l,l00 F.Gaseous regeneration products which include nitrogen and carbon dioxideare removed from the system at 9 by way of heat exchangers l0 and 11 andpass from the system at 12. Liquid water is passed by 13 and 14 throughheat exchangers 11 and 10 resulting in steam which can be used in theprocess and which is obtained at 15.

From cracking reaction zone 5 a cracked effluent is passed by 20 throughheat exchanger 3 and 21 into a gas separatorcooling zone 22 from thebottom of which a cycle oil containing essentially C and heavierhydrocarbons is returned by way of 2, heat exchanger 3 and 4 to cracker5.

Non-condensed gases are removed from separator 22. These gases whichcontain hydrogen and C -C, hydrocarbons, both saturated and unsaturatedare passed by 23 to the suction of cracked gas compressor 24 and by 25to catalytic hydrodesulfurization in a nickel molybdatehydrodesulfurization catalyst containing vessel 26. Here thenon-condensed gases and vapors are at least partially desulfurized andare passed by 27 cooler 28 and 29 to gas separator zone or vessel 30. Aportion of non-condensed gas is taken from vessel 30 by 31 andcompressor 32 and recycled as a hydrogen-rich gas to vessel 26 to aid inthe desulfurization there taking place. The liquid phase from vessel 30is passed by 34, 35, preheater 36, 37 and 38 to a synthetic natural gasproducing reactor 39 to which steam obtained at is passed by 16.Preferably, however,,the stream in 37 is preheated at 41 and passed by47 into and through a 'zinc oxide bed 48 and thence by 49 as a sulfurfree stream to reactor 39. The stream in 49 normally will contain lessthan about one part per million of sulfur.

Returning to gas separator 30 a portion of the hydrogen-rich gas ispassed by 50 into an H 8 removal unit of the Girbotol type. Thisconsists essentially of an absorber 51 to which is passed, into the top,a hydrogen sulfide removal solvent or absorbent such as an aqueoussolution of monoethanolamine. The enriched solution is passed by 52 tostripper 53 wherein it is heated and stripped of 1-1 8 which is removedfrom the system at 54. The lean solvent, after suitable temperatureadjustment not shown, is passed by 55 to the top of the absorber. The HS-free gas in 35 is passed together with the liquid from 34 to thesynthetic natural gas reactor as earlier described. A synthetic gasproduct is removed at 57 passed through heat exchanger 41 and by 42,after cooling at 43 from the process as product gas obtained at 44.Steam is generated in cooling the synthetic natural gas stream by liquidwater introduced at 45 into heat exchanger 43 and recovered therefrom assteam is passed by 46 to 16 and thence to the synthetic natural gasreactor as a portion of the steam requirement there.

Properties of Feed to Cat Cracker lJnit West Texas Atmospheric Gas Uponcracktng under conditions as noted below in the table the effluentpresented analysis as also follows.

Average Temperature, F. 898

Pressure, psig 10 Process Cycles, per minute 14 Steam, Pounds/Barrel19.7

Conversion. Volume Fresh Feed 52.34

Severity Factor 5.94

Weight of Moles/100 Lbs.

Yield Fresh Feed of Fresh Feed G soline (C -C Cycle Oil 48.20

Coke 13.91

Gasoline. ASTM (C,-,C,, hydrocarbons) Cycle Oil FD I04F 2% 492F 10 13610 522 20 156 20 554 30 182 30 583 40 214 40 610 60 290 60 658 352 80725 EP 432 826 Gravity, AP1 51.4 26.8

Bromine Number 78 Sulfur,-Wt. .86

Carbon Residue .16

K Factor 1 1.51

Moles Olefin/ Lbs. Fresh Feed 0.130

Typical'crude oils which can be used as feedstock in this inventioninclude paraffinic-base, naphthenic-base, asphaltic-base or mixed basecrude oils, or fractions of the crude oil. Gas oils and distillatesboiling above about 400 F are now preferred as feedstock in thisinvention.

The foregoing information and data which have been given to illustratethe operation of the invention are inclusive of actual data obtained inruns which are characterized, knowledge in the field and engineering andrelated information. These have been incorporated together to more fullyillustrate the invention.

Reasonable variation and modification are possible in the scope of theforegoing disclosure, the drawing and the appended claims to theinvention the essence of which is that there has been provided acombination of steps for producing a synthetic natural gas or fuel froma hydrocarbon oil in a manner and under conditions such that the processis self-sustaining in hydrogen, heat requirements for producing steam,does not require hydrogen to be produced in a separate step, yieldingsaid gas or fuel in a simplified operation which comprises essentiallythe cracking of the oil under conditions of severity to produce optimumamount of C and lighter products using a high metal content usedcracking catalyst, hydrotreating C and lighter products thus obtained,using hydrogen produced in the process to hydrogenate the olefinscontained in the gases and to hydrodesulfurize the same, passing gasesthus treated to further treatment to remove hydrogen sulfide therefrom,passing thus pretreated gas and liquid, obtained from thehydrodesulfurization step upon cooling the hydrodesulfurizationeffluent, to a Synnat reaction operation and recovering from saidoperation a synthetic natural gas or fuel.

I claim: 1. The production of a synthetic natural gas or fuel whichcomprises in combination the steps as follows:

1. catalytically cracking a hydrocarbon oil in presence of a high metalscontent cracking catalyst under conditions to produce an optimum maximumof C and lighter products, 2. hydrodesulfurizing said products, 3.separating said products into a liquid fraction and a hydrogen-rich gas,4. using a portion of the hydrodesulfurization, 5. removing hydrogensulfide from the remainder of said hydrogen-rich gas, and 6. passingthus treated hydrogen-rich gas together hydrogen-rich gas for said 3. Anoperation according to claim 1 wherein the catalyst used in the crackingoperation is regenerated and heat obtained from the regeneration is usedto produce steam for the Synnat operation.

4. An operation according to claim I wherein the liq-' uid and gas priorto being passed to the Synnat operation are treated to produce a streamcontaining less than one part per million of sulfur and such a stream ispassed to the Synnat operation.

1. THE PRODUCTION OF A SYNTHETIC NATURAL GAS OR FUEL WHICH COMPRISES INCOMBINATION THE STEPS OF FOLLOWS:
 1. CATALYTICALLY CRACKING AHYDROCARBON OIL IN PRESENCE OF A HIGH METALS CONTENT CRACKING CATALYSTUNDER CONDITIONS TO PRODUCE AN OPTIMUM MAXIMUM OF C12 AND LIGHTERPRODUCTS,
 2. An operation according to claim 1 wherein C12 and higherboiling products obtained from the cracking are recycled to saidcracking.
 2. hydrodesulfurizing said products,
 2. HYDRODESULFURIZINGSAID PRODUCTS,
 3. SEPARATING SAID PRODUCTS INTO A LIQUID FRACTION AND AHYDROGEN-RICH GAS,
 3. An operation according to claim 1 wherein thecatalyst used in the cracking operation is regenerated and heat obtainedfrom the regeneration is used to produce steam for the Synnat operation.3. separating said products into a liquid fraction and a hydrogen-richgas,
 4. An operation according to claim 1 wherein the liquid and gasprior to being passed to the Synnat operation are treated to produce astream containing less than one part per million of sulfur and such astream is passed to the Synnat operation.
 4. using a portion of thehydrogen-rich gas for said hydrodesulfurization,
 4. USING A PORTION OFTHE HYDROGEN RICH GAS FOR SAID HYDRODESULFURIZATION,
 5. REMOVING HYDROENSULFIDE FROM THE REMAINDER OF SAID HYDROGEN-RICH GAS, AND
 5. removinghydrogen sulfide from the remainder of said hydrogen-rich gas, and 6.passing thus treated hydrogen-rich gas together with liquid obtainedfrom the hydrodesulfurization operation to a Synnat or synthetic naturalgas producing operation.
 6. PASSING THUS TREATED HYDROGEN-RICH GASTOGETHER WITH LIQUID OBTAINED FROM THE HYDROESULFURIZATION OPERATION TOA SYNNAT OR SYNTHETIC NATURAL GAS PRODUCING OPERATION.